A typical razor cartridge is composed of blades and a blade housing, generally including one or more seats onto which the blades get seated. The blades are seated on the seats, and a single razor cartridge is formed by using a clip for wrapping, i.e., coupling firmly, the blades and the blade housing to allow the blades to be fixed.
The blade housing may be provided with a single seat for mounting a single blade, although a pervasive trend in the razor cartridge art is to form a plurality of seats for multiple blades, positioned in a close arrangement, to allow body/facial hairs to be repeatly and reliably cut.
The seat is generally integrally formed with the blade housing and fixes the blades to the blade housing such that the seat engages the rear end of each blade opposite its cutting edge. Accordingly, the interval or spacing between the plurality of blades is determined according to the interval in which the seats are arranged. The spacing between the plurality of blades is referred to as a “span.”
In designing a razor cartridge, determining a proper span is an important issue. If the span is too large, it may facilitate the cleaning of the sludge, which is the residue from the hair cutting process, but it may also increase skin irritation. If the span is too small, although it may lead to skin irritation being reduced, it may also lead to insufficient cleaning of the sludge.
There are advantages and disadvantages depending on the span value and the preferred span value for each user may be different. However, as described above, the blade housing of a razor cartridge is generally formed so that once determined, a span value becomes unchangeable, making it impossible to customize the razor cartridge according to the user's needs or preference.